The present invention relates to a multiplexed analog-to-digital converter, and particularly to a multiplexed analog to digital converter having a feedback stabilized ramp.
The converter according to the invention is a multi-channel, multiplexed analog-to-digital converter with day-to-day bias stability in the sub-microvolt range. A primary application is found in digitization of restoring currents in the gyro and accelerometer control loops of inertial guidance systems.
A prior art, analog-to-digital converter is shown in U.S. Pat. No. 3,389,271 of inventor J. W. Gray, issued June 18 1968, and assigned to the same assignee as this invention. In such a converter the unknown current is divided through a sense resistor and through a summing resistor to an electronic integrator which is reset by current pulses of precisely known charge. This is classed as voltage-to-frequency (V/F) converter.
The problem of the prior art device is that it employs precision balancing pulses which are normally long with respect to rise and fall time of analog switching devices, thus limiting maximum pulse frequency, hence resolution.